Jack and Kate spent tense moments in the jungle, gathering firewood and breaking it into usable pieces, and during their angry silence and the following conversation, they broke a total of 8 branches. ("One of Us")

Miles told Michael, "80% of the people on this boat are lying about something." ("Meet Kevin Johnson")

The number 8 appeared twice on the number plate of the taxi that Ben was in when he went to visit Charles Widmore in London. (Incidentally, the car behind the taxi when it stopped had the number 8 on it.) ("The Shape of Things to Come")

1) when his father pushed him out of the window and he was paralyzed.
2) when the trebuchet he and Boone had made broke and stabbed his right leg.
3) when he lost feeling in his legs in the episode Deus Ex Machina.
4) when he purposely injured his legs to test for feeling
5) when his legs were crushed by the lockdown blast-door.
6) when he lost feeling in his legs after Ben shot him in Season 3.
7) when he was shot by Ethan during the time-flashes.
8) when he suffered a compound fracture when he fell down the well